The present device is an improvement of a water heater control system patented Apr. 5, 1977, U.S. Pat. No. 4,016,402 by the applicant of the instant invention.
The purpose of the control system in that device was to raise the setting of a thermostat which controlled the water heater during periods of high water use, and lower the thermostat during times of low hot water demand, such as in the night and early morning hours.
The advantage of adjusting the temperature of this fashion is two-fold. First, the energy dissipated as waste from the system is of course reduced if the temperature is lower. The second advantage, which although perhaps being secondary from an ecological standpoint is paramount in economics, is the considerable reduction of the rate of boiler scale formation, which rises dramatically with an increased temperature over 100.degree.. Ordinarily, the boiler scale is in the end of the nemesis of most water heater systems, and inefficiency in heat transfer caused by the scale creates additional heat losses prior to the complete disutility of the unit.
The above referenced unit is quite advantageous compared to existing hot water heating control systems (ordinarily simply a thermostat), but under certain circumstances was subject to the following operational limitation. During periods of low hot water demand, the thermoswitch of that device would respond to the warm temperature in the recirculatory system by lowering the thermostat, which it should properly do. However, with the thermostat in the lowered mode the temperature in the recirculatory system would drop just as it does during periods of high water use (although much slower), and eventually would trigger the thermoswitch just as would low temperature caused by high water demand, thus elevating the thermostat in the middle of the night in response to a signal other than low water usage.